Ceramic powders and metal powders can be formed into desired shapes, and then sintered to form dense bodies that can be structural. Such forming methods offer rapid manufacturing of net-shape parts. The sintering shrinkage of typical metal powders is about 6%, while shrinkage of typical ceramic powders is about 1%. Furthermore, ceramics require much higher sintering temperatures than metals. These disparities, plus different thermal expansion rates, make bonding of ceramics to metals difficult. However, such bonding is needed in order to provide ceramic coatings or layers on metal components for gas turbine engine applications, where the ceramic coating serves as a thermal barrier and/or provides object impact resistance and/or imparts desirable abrasion characteristics. Some gas turbine components can be exposed to temperatures that cycle from ambient temperatures to about 1,500° C. between shut-down and operational phases of the gas turbine.
Joining of ceramic coatings to metal substrates is known to be done by surface deposition techniques such as High Velocity Oxygen Fuel spraying (HVOF), Air Plasma Spraying (APS), and Physical Vapor Deposition (PVD). These methods provide a non-chemical bond that has somewhat limited bond integrity. The difference in thermal expansion between a metal substrate and a ceramic layer can limit the temperature range that such a bi-layer material system can withstand before strain-induced delamination or deformation occurs.